This invention relates to a cover for a furnace incorporating a spray cooling system.
Electric furnaces of various types such as electric-arc, plasma-torch and resistance heating furnaces are being used for melting and refining metals as well as for melting discarded materials. These electric furnaces are generally comprised of a main body and a cover therefor. Recently, consideration is being given to covers for such furnaces incorporating a system for spray cooling, being of a hollow double-layered structure with a space in between and provided with nozzles in this hollow space for spraying coolant such as water therethrough such that the cover can be efficiently cooled thereby. This invention relates to improved furnace covers of this type.
U. S. Pat. Nos. 4,715,042 and 4,813,055 and Japanese Patent Publication Tokkai 3-75493, for example, have recently disclosed furnace covers incorporating a spray cooling system, being of a hollow double-layered structure with a space in between and provided with a plurality of nozzles in this space and a water outlet to which a vacuum pump can be connected through a hose such that the cooling water sprayed from these nozzles into the hollow space can be forcibly removed from the interior by the pump through the water outlet and the hose. Furnace covers of this type are disadvantageous because vacuum pumps are expensive and require a large space. Moreover, the cooling of the cover becomes uneven as the furnace is used repeatedly many times, and the overall cooling efficiency is deteriorated. This is because materials such as scraps and discarded substances as well as splashed materials, slag and dust become attached and/or solidified between the main body of the furnace and the cover as the furnace is used many times, causing the cover to become sloped accordingly. If this happens, the cooling water sprayed over the inner walls of the hollow space becomes collected in a corner in the direction of which the cover is sloped and a portion of the inner wall of the hollow space becomes covered by the collected water. In this situation, the original purpose of spray cooling, which is to cool the cover by spraying cooling water thereon to thereby remove heat therefrom by heat transfer therethrough, can no longer be accomplished, and the portion of the cover where water is collected inside the hollow space cannot be cooled as efficiently as the other portions.